X-ray fluorescence analysis of nickel in the upper twenty-four inches of residual soils on a 500 foot by 500 foot grid over the Cuyamaca Gabbro reveals anomalies up to about 600 ppm over a regional background of about 70 ppm. A tentative threshold for anomalies associated with mineralization is established at 200 ppm. Anomalies display subadjacent mechanical dispersion patterns over nickeliferous gossans developed on pyrrhotite-pentlandite mineralization. Mineralization is apparently controlled by a conjugate system of faults or fractures and is localized around the periphery of the pluton. Statistical grouping of the nickel values results in an approximately log-normal distribution both in local as well as regional studies. Direct x-ray fluorescence analysis of nickel in leaves of the oak Quercus chrysolepsis may provide an alternative method of measuring nickel distribution in the soils of the area.
